Morphogenetic influences on rubber content and molecular weight in tissue cultures of guayule

Abstract

A gel permeation chromatographic (GPC) method was developed for measuring the content and M r s of cis-polyisoprene in tissue cultures of guayule ( Parthenium argentatum). Rubber production and growth rates were investigated in several morphogenetically distinct cultures, including normal and crown gall callus, and root and shoot cultures. These results were compared with rubber production in leaves and stems of whole plants. Tissue cultures yielded 1 to 10% of the rubber found in mature guayule stem tissue. The M r distributions of rubber from cultures were bimodal in contrast with that of rubber from whole plant stems which is unimodal. In the intact plant only the rubber from leaf tissue is bimodal with most of it contained in a M r fraction with a peak of 22 300. In contrast, the rubber peak in stems of young guayule plants was 500 000. Rubber from shoot and root cultures had average M r s of 150000 and 201 000 respectively, and normal and tumour callus cultures had M r s of 415 000 and 291 000. The ability of tissue cultures to make comparatively high M r rubber relative to whole plants supports the use of guayule tissue cultures for studies of rubber biosynthesis.